Patterns of electrically conducting polymers and their application as electrodes or electrical contacts

ABSTRACT

Electronic devices having patterned electrically conductive polymers providing electrical connection thereto and methods of fabrication thereof are described. Liquid crystal display cells are described having at least one of the electrodes providing a bias across the liquid crystal material formed from a patterned electrically conductive polymer. Thin film transistors having patterned electrically conductive polymers as source drain and gate electrodes are described. Light emitting diodes having anode and coated regions formed from patterned electrically conductive polymers are described. Methods of patterning using a resist mask; patterning using a patterned metal layer; patterning the metal layer using a resist; and patterning the electrically conductive polymer directly to form electrodes and anode and cathode regions are described.

This application claims priority from, and is a continuation-in-part of,International Application No. PCT/US97/20862 filed on Nov. 10, 1997 andpublished on May 22, 1998, the teaching of which is incorporated hereinby reference.

This application is a continuation-in-part of copending U.S. applicationSer. No. 08/476,141 filed Jun. 7, 1995 entitled, “ElectricallyConductive and Abrasion/Scratch Resistance Polymeric Materials and UsesThereof ” to Angelopoulos et al., the teaching of which is incorporatedherein by reference. U.S. application Ser. No. 08/476,141 is a divisionof U.S. application Ser. No. 08/193,926 now issued as U.S. Pat. No.5,721,299 which is a continuation-in-part of and incorporated byreference U.S. application Ser. No. 08/357,565 filed May 26, 1989 issuedas U.S. Pat. No. 5,198,153. Thus, the teaching of U.S. application Ser.No. 08/357,565 filed May 26, 1989 is incorporated herein by reference.U.S. application Ser. Nos. 08/476,141 and 08/357,565 teach electricallyconductive compositions, structures and methods useful to practice thepresent invention.

This application is a continuation-in-part of copending U.S. applicationSer. No. 09/036,458 filed Mar. 6, 1998 entitled, “Methods of Processingand Synthesizing Electrically Conductive Polymers and Precursors Thereofto Form Electrically Conductive Polymers having High ElectricalConductivity”, the teaching of which is incorporated herein byreference. This application teaches highly conductive polymers andmethods of fabrication useful to practice the present invention.

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,129 filed Mar.7, 1997 entitled, “Method of Patterning Electrically Conductive PolymerFilms to Form Electrodes and Interconnection Conductors on a SurfaceUsing a Resist to Pattern a Metal Layer to Pattern an ElectricallyConductive Polymer Layer”, the teaching of which is incorporated hereinby reference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/030,501 filed Nov.12, 1996 entitled, “SOLUTION APPLIED, IMAGEABLE, TRANSPARENT POLYMERS ASCONDUCTING ELECTRODES” to M. Angelopoulos et al., the teaching of whichis incorporated herein by reference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,335 filed Mar.7, 1997 entitled, “PATTERNS OF ELECTRICALLY CONDUCTING POLYMERS ANDTHEIR APPLICATION AS ELECTRODES AND ELECTRICAL CONTACTS” to M.Angelopoulos et al., the teaching of which is incorporated herein byreference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,628 filed Mar.7, 1997 entitled, “PATTERNS OF ELECTRICALLY CONDUCTING POLYMERS ANDTHEIR APPLICATION AS ELECTRODES IN FIELD EFFECT TRANSISTORS” to M.Angelopoulos et al., the teaching of which is incorporated herein byreference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,159 filed Mar.7, 1997 entitled, entitled, “METHODS OF PATTERNING ELECTRICALLYCONDUCTIVE POLYMER FILMS TO FORM ELECTRODES AND INTERCONNECTIONCONDUCTORS ON A SURFACE” to M. Angelopoulos et al., the teaching ofwhich is incorporated herein by reference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,130 filed Mar.7, 1997 entitled, “Method of Patterning Electrically Conductive PolymerFilms to Form Electrodes and Interconnection Conductors on a SurfaceUsing a Resist Mask”, the teaching of which is incorporated herein byreference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,132 filed Mar.7, 1997 entitled, “STRUCTURES HAVING PATTERNED ELECTRICALLY CONDUCTIVEPOLYMER FILMS AND METHODS OF FABRICATION THEREOF” to M. Angelopoulos etal., the teaching of which is incorporated herein by reference, and

This application claims priority from, through the claim of priority ofPCT/US97/20862, Provisional Application Ser. No. 60/040,131 filed Mar.7, 1997 entitled, “LIGHT EMITTING DIODES HAVING ELECTRICALLY CONDUCTIVEPOLYMER ELECTRODES” to M. Angelopoulos et al., the teaching of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed to patterned electrically conductingpolymers and methods of fabrication thereof. More particularly thepresent invention is directed to electronic devices having electricallyconductive polymers as electrode contacts and active regions andpatterned electrical contacts formed from electrically conductivepolymers, in particular the application of these polymers as electrodesor electrical contacts for electro-optical transducers such as liquidcrystal displays, electro-optical modulators, diodes, light emittingdiodes, transistors, and the like.

BACKGROUND

The electrical contacts or electrodes in current electro-opticaltransducers and other devices are generally metals. Metals are depositedby evaporative or sputtering processes which require expensive toolingand overall are a cumbersome processes.

Electrically conducting polymers are a relatively new class ofelectronic materials which are taught herein as candidates for electrodematerials. These polymers combine the electrical properties of metalswith the processing advantages of polymers.

Herein we describe examples of electrically conductive polymers such assubstituted and unsubstituted electrically conducting polyanilines,polyparaphenylenes, polyparapheylenevinylenes, polythiophenes,polyfurans, polypyrroles, polyselenophenes, polyisothianapthenes,polyphenylene sulfides, polyacetylenes, polypyridylvinylenes,polyazines, combinations thereof and blends thereof with other polymersand copolymers of the monomers thereof.

In order for these polymers to be used as an electrode in a device theypreferably have suitable electrical conductivity and be easilypatternable. In addition, these polymers preferably do not outgascausing contamination of the devices to which they provide electricalcontact. Furthermore, the conducting polymers are preferably patternableby lithography. Patterning preferably does not result in a decrease inthe electrical conductivity of the polymer nor cause any deteriorationof the properties of the electrically conducting polymer.

It is therefore desirable to develop methods of patterning thesepolymers so that they can be used on any conducting polymer system andwithout negatively impacting the conducting polymer so that thepatterned electrically conductive polymer can be used as an electricalcontact to a device. It is also desirable that the conducting polymerproperties be controlled so that outgassing or contamination of thedevices does not occur.

OBJECTS

It is an object of the present invention to provide improved electronicdevices using electrically conductive polymers.

It is an object of the present invention to provide patterns ofelectrically conductive polymers and methods of fabrication thereof. Inparticular, a resist is first patterned and the resist pattern issubsequently transferred to the conducting polymer. Once the pattern istransferred to the conducting polymer, the result is removed.

It is an object of the present invention to provide patterns ofelectrically conductive polymers by the use of a resist which is appliedto the conducting polymer. In particular, the metal is first patternedand the metal pattern is subsequently transferred to the conductingpolymer followed by removal of the metal.

It is another object of the present invention to provide patterns ofelectrically conducting polymers by the use of a metal which is appliedto the conducting polymer.

It is another object of the present invention to provide patterns ofelectrically conducting polymers having high electrical conductivity.

It is another object of the present invention to provide patterns ofelectrically conducting polymers having high optical transmission.

It is another object of the present invention to provide patterns ofelectrically conducting polymers having good thermal stability.

It is another object of the present invention to provide electricallyconducting polymers having high optical transmission and high electricalconductivity.

It is another object of the present invention to provide electricallyconducting polymers and patterns of electrically conducting polymersthat can be used as electrical contacts or electrodes.

It is another object of the present invention to provide electricallyconducting polymers and patterns of electrically conducting polymersthat can be used as electrical contacts or electrodes in electro-opticaltransducers and devices.

It is another object of the present invention to provide electricallyconducting polymers and patterns of electrically conducting polymersthat can be used as electrodes in liquid crystal displays.

It is another object of the present invention to provide a liquidcrystal display comprising electrically conducting polymer electrodes.

It is another object of the present invention to provide a liquidcrystal display comprising electrically conducting polymer electrode anda metal electrode

It is another object of the present invention to provide a liquidcrystal display comprising electrically conducting polymer electrode andan indium tin oxide electrode.

It is another object of the present invention to provide an activematrix thin film transistor (TFT) liquid crystal display consisting ofone or more electrically conducting polymer electrode.

It is another object of the present invention to provide a liquidcrystal display comprising one or more electrically conducting polymerelectrode which exhibits good charge retention.

It is another object of the present invention to provide a liquidcrystal display comprising one or more electrically conducting polymerelectrodes which exhibits good transmission/voltage characteristics.

It is another object of the present invention to provide a liquidcrystal display comprising one or more electrically conducting polymerelectrode which exhibits good image sticking characteristics.

It is another object of the present invention to provide electricallyconducting polymers and patterns of electrically conducting polymersthat can be used as one or more electrode in light emitting diodes.

It is another object of the present invention to provide organic orinorganic light emitting diodes comprising one or more electricallyconducting polymer electrodes.

It is another object of the present invention to provide organic orinorganic light emitting diodes consisting of one or more patternedelectrically conducting polymer electrodes.

It is another object of the present invention to provide light emittingdiodes having hole injection and/or electron injecting regions formedfrom electrically conductive polymers.

It is another object of the present invention to provide electricallyconducting polymers and patterns of electrically conducting polymersthat can be used as electrical contacts to transistors such as one ormore of the drain source and gate electrodes in field effect transistor(FET) devices and contacts to bipolar transistors.

It is another object of the present invention to provide patterns ofelectrically conducting polymers that exhibit good conductivity, goodthermal stability, no outgassing, and in certain cases high opticaltransmission.

It is another object of the present invention to provide patterns ofelectrically conducting polymers by the application of a resist on theconducting polymer whereby the resist is exposed and developed forming apattern in the resist. The resist pattern is transferred to theconducting polymer by etching followed by removal of the resist.

It is another broad aspect of the present invention to provide patternsof electrically conducting polymers by the application of a metal on theconducting polymer surface. The metal is patterned by the application ofa resist which is exposed and developed. The resist pattern istransferred to the metal followed by pattern transfer to the conductingpolymer by etching techniques.

It is another broad aspect of the present invention to provide patternsof electrically conducting polymers by the application of a patternedmetal layer on the conducting polymer, etching of the pattern into theconducting polymer and removal of the metal.

It is a more particular aspect of the present invention to provide a TFTswitch for liquid crystal displays in which one or more of the source,drain and gate electrodes comprise electrically conducting polymerexhibiting good conductivity and good thermal stability.

It is another object of the present invention to provide a lightemitting diode consisting of an electrically conducting polymerelectrode and a metal electrode.

It is another object of the present invention to provide electricallyconducting polymers and patterns of electrically conducting polymersthat can be used as one or more electrodes in light emitting diodes.

It is another object of the present invention to provide organic orinorganic light emitting diodes consisting of one or more electricallyconducting polymer electrodes.

It is another object of the present invention to provide organic orinorganic emitting diodes consisting of one or more patternedelectrically conducting polymer electrodes.

It is another object of the present invention to provide a lightemitting diode comprising a conducting polymer as a hole injectingelectrode or as an electron injecting layer.

SUMMARY OF THE INVENTION

Accordingly, it is a broad aspect of the present invention to provideelectrical conductive polymers and patterned electrically conductingpolymers and to provide methods of patterning thereof.

It is a broad aspect of the present invention to provide an electronicdevice having a patterned electrically conductive polymer providingelectrical connection to the device.

It is a broad aspect of the present invention to dispose a patternedelectrically conductive polymer on an electronic device to provideelectrical contact to the device.

It is another broad aspect of the present invention to provide patternsof electrically conducting polymers that exhibit good conductivity, goodthermal stability, no outgassing, and in certain cases high opticaltransmission.

It is another broad aspect of the present invention to provide patternsof electrically conductive polymers by the application of a resist onthe conducting polymer where the resist is exposed and developed and thepattern is transferred to the conducting by etching techniques followedby removal of the resist.

It is another broad aspect of the present invention to provide patternsof electrically conducting polymers by the application of a metal on theconducting polymer surface. The metal is patterned by an application ofa resist which is exposed and developed. The resist pattern istransferred to the metal followed by transfer to the electricallyconducting polymer by etching techniques followed by removal of themetal.

It is another broad aspect of the present invention to provide patternsof electrically conductive polymers by the application of a patternedmetal layer on the electrically conductive polymer followed by etchingof the pattern into the electrically conducting polymer and removal ofthe metal.

It is another broad aspect of the present invention to provideelectrically conducting polymers and patterns of electrically conductingpolymers as electrical contacts to electro-optical transducers anddevices.

It is another broad aspect of the present invention to provideelectro-optial transducers and devices having one or more electricallyconducting polymer electrodes.

It is a more particular aspect of the present invention to provide aliquid crystal display having one or more electrically conductingpolymer electrodes. In one embodiment the liquid crystal display has anindium tin oxide electrode and an electrically conducting polymerelectrode.

It is a more particular aspect of the present invention to provide aliquid crystal display having one or more electrically conductivepolymer electrodes exhibiting high charge retention, goodtransmission/voltage characteristics, and good image stickingproperties.

A more particular aspect of the present invention is an electronicdevice having an electronically active portion having a surface; thesurface has a dielectric layer having an opening having a perimetertherein exposing the electronically active portion; a layer ofelectrically conductive polymer is disposed on the dielectric layer; thelayer of electrically conductive polymer electrically contacts theelectronically active portion through the opening and overlapping theperimeter to be disposed on the dielectric layer.

Another more particular aspect of the present invention is a liquidcrystal display structure having:

a first substrate;

a second substrate;

a liquid crystal layer disposed between the first substrate and thesecond substrate;

at least one of the first substrate and the second substrate has anelectrically conductive polymer disposed thereon providing means forapplying an electrical potential across the liquid crystal layer.

Another more particular aspect of the present invention is field effecttransistor having source, drain and gate electrodes at least one ofwhich is a patterned electrically conductive polymer.

Another more particular aspect of the present invention is a structurehaving:

a substrate;

a patterned electrically conductive polymer gate disposed on thesubstrate;

the gate being an electrically conductive polymer;

an insulating layer disposed on the patterned gate;

a patterned source electrode disposed on the insulating layer;

a patterned drain electrode disposed on the insulating layer;

the patterned source electrodes and the patterned drain electrodes beingformed from an electrically conductive polymer; and

a semiconducting material disposed in the patterned source and patterneddrain and the gate between the patterned source and said patterneddrain.

Another more particular aspect of the present invention is alight-emitting diode having: a substrate, an anode structure, anelectroluminescent region, and a cathode structure wherein the cathodestructure or the anode structure is an electrically conductive polymer.

Another more particular aspect of the present invention is an organiclight emitting diode having:

a substrate, an anode, an organic electroluminescent layer and acathode, the anode or cathode in this structure being an electricallyconducting polymer.

Another more particular aspect of the present invention is a method of:

providing a substrate having a layer of an electrically conductivepolymer material;

disposing on the layer of electrically conductive polymer material aresist layer;

exposing the resist to a pattern of energy;

developing the pattern of radiation forming a pattern in the resistcomprising covered and uncovered regions of said electrically conductivepolymer; removing the electrically conductive polymer in the uncoveredregions, and removing the resist leaving a pattern of said electricallyconductive polymer.

Another more particular aspect of the present invention is a method of:

providing a substrate having a layer of electrically conductive polymermaterial;

depositing a pattern of a metal layer through a metal mask forming apatterned metal layer on the layer of electrically conductive polymer,forming regions of the electrically conductive polymer covered by themetal pattern and uncovered regions of the electrically conductivepolymer, etching the uncovered regions to remove the exposedelectrically conductive polymer regions; and removing the metalresulting in a pattern of an electrically conducting polymer.

Another more particular aspect of the present invention is a method of:

providing a substrate having a layer of an electrically conductivepolymer;

disposing a layer of metal on the layer of electrically conductivepolymer; disposing a resist on the metal layer;

exposing the resist to pattern of radiation;

developing the pattern of radiation forming a pattern in the resistresulting in covered and uncovered regions of the metal layer;

removing the metal layer in said uncovered regions, resulting in coveredand uncovered regions of said electrically conductive polymer;

removing the uncovered regions of said electrically conductive polymer;

removing the resist; and

removing remaining portions of the metal layer resulting in a pattern ofan electrically conducting polymer.

Another more particular aspect of the present invention is a method of:

providing a substrate having a layer of an electrically conductivepolymer material;

wherein the electrically conductive polymer contains energy sensitiveconstituents;

exposing the electrically conductive polymer to a pattern of energyforming a pattern of exposed and unexposed regions; and

removing the electrically conductive polymer in one of the exposed andunexposed regions to form a pattern of said electrically conductivepolymer on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features, and advantages of the present invention willbecome apparent from a consideration of the following description of theinvention when in conjunction with the drawings FIGS. in which:

FIG. 1 is a schematic perspective view of an exemplary embodiment of astructure according to the present invention including a patternedelectrically conductive polymer.

FIG. 2 is a schematic side view of another exemplary embodiment of astructure according to the present invention including a patternedelectrically conductive polymer.

FIG. 3 is a schematic of a typical liquid crystal configuration.

FIG. 4 is a schematic of the operation of a twisted nematic liquidcrystal cell; in (a) voltage is applied and the transmission of the cellis maximum whereas in (b) a voltage is applied and the transmission ofthe cell is minimum.

FIG. 5 is a schematic of a typical active matrix thin film transistordisplay.

FIG. 6 shows a top view of a unit cell of a TFT/LCD display.

FIG. 7 shows a cross-section along line AA′ of FIG. 6.

FIG. 8 shows another cross-section along line AA′ of FIG. 6.

FIG. 9 shows part of the assembled liquid crystal display.

FIG. 10 shows a schematic of the cross section of a TFT in which one ormore of the source drain, and the gate electrodes comprise a conductingpolymer. The source and drain are disposed directly on top of the gateinsulator and subsequently they are covered by the semiconductor.

FIG. 11 shows a schematic of the cross section of a TFT in which one ormore of the source and the drain electrodes comprise a conductingpolymer. The substrate is conductive and used as the gate electrode too.The source and drain electrodes are disposed directly on the insulatorand subsequently they are covered by the semiconductor.

FIG. 12 shows a schematic of a cross section of a TFT in which one ormore of the drain, and the gate electrodes comprise a conductingpolymer. The source and drain electrodes are disposed directly on top ofthe semiconductor.

FIG. 13 shows a schematic of the cross section of a TFT in which one ormore of the source and the drain electrodes comprise a conductingpolymer. The substrate is conductive and used as the gate electrode. Thesource and drain electrodes are disposed directly on the semiconductor.

FIG. 14 shows a plot of the current flowing between the source and thedrain of the TFT device, whose structure is schematically drawn in FIG.11, versus the voltage gate electrode. The channel length, L, of thisdevice was 100 microns and the channel width was 1500 microns.

FIG. 15 shows the top view of a typical layout of a TFT based activematrix liquid display. One or more of the source, the drain, and thegate electrodes comprise a polymer.

FIG. 16 shows cross sections of a pixel of a TFT based active matrixliquid crystal display having two different TFT configurations, FIG.16(a) and FIG. 16(b). One or more of the source, the drain, and thecomprise a conducting polymer.

FIG. 17 shows contact via through a passivating or insulating layer. Thebottom is a conducting polymer. The top layer could be either the samematerial or a different conducting material such as a metal, or ITO.

FIG. 18 shows a prior art OLED structure on a glass substrate with anopaque cathode on top wherein light is emitted from the glass side only.

FIG. 19 generally shows an LED structure of the present invention with atransparent (or opaque) cathode.

FIG. 20 shows schematically LED arrays for displaying an image with FIG.20A that of a passive matrix having an LED at the crosspoint of each rowand column and FIG. 20B being that of an active matrix with a currentregulating circuit at the crosspoint of each row and column line.

FIG. 21 depicts the patterning of conducting polymers by the applicationof a resist on the surface of the conducting polymer. The resist isexposed and developed; the pattern is transferred to the conductingpolymer; the resist is removed.

FIG. 22 depicts the patterning of conducting polymers by the applicationof a patterned metal layer on the conducting polymer via a metal mask.The pattern is transferred to the conducting polymer followed by removalof the metal.

FIG. 23 depicts the patterning of conducting polymers by the applicationof a blanket metal layer on the conducting polymer. The metal ispatterned by a resist; the pattern is transferred first to the metal andthen to the conducting polymer by etching; the remaining resist andmetal are removed.

FIG. 24 depicts the patterning of a conducting polymer directly byexposing it to radiation; the polymer is subsequently developed toremove the more soluble regions.

FIGS. 25 and 26 depict conducting polyaniline lines on the order of 10&mu.m delineated with the use of a resist on the surface of theconducting polymer.

FIGS. 27 and 28 show conducting polyaniline lines fabricated with theuse of metal deposited on the surface of the conducting polymer througha metal mask.

FIGS. 29, 30 and 31 depict conducting polyaniline lines fabricated withthe use of blanket metal deposited on the surface of the conductingpolymer which was imaged with the use of a resist.

FIG. 32 depicts the optical transmission spectrum for a 500 Angstromfilm of polyaniline.

FIG. 33 shows the transmission/voltage characteristics for a liquidcrystal display made with 2 polyaniline electrodes.

FIG. 34 shows the brightness (transmission)/voltage characteristics fora liquid crystal display made with 2 ITO electrodes.

FIG. 35 shows the voltage vs. time curve for a liquid crystal displaymade with polyaniline electrodes. The charge retention is over 95%.

FIGS. 36 and 37 are schematic diagrams of joints between a non-polymericelectrical conductor and a polymeric electrical conductor.

FIG. 38 is a schematic diagram of a bipolar transistor having electrodesaccording to the present invention.

DETAILED DESCRIPTION

The present invention is directed to devices using electricallyconducting polymers including substituted and unsubstitutedpolyanilines, polyparaphenylenes, polyparaphenylene vinylenes,polythiophenes, polypyrroles, polyfurans, polyselenophenes,polyisothianapthenes, polyphenylene sulfides, polyacetylenes,polypyridyl vinylenes, combinations thereof and blends thereof withother polymers, copolymers of the monomers thereof. It is found thatthese polymers can be patterned lithographically to form electricallyconductive patterns which can act as electrodes or electrical contactsin various electro-optical transducers and devices. The presentinvention is also directed to electro-optical transducers and devicesconsisting of one or more electrically conductive polymer electrodes.

FIG. 1 schematically shows in perspective substrate 200 having patternedelectrically conductive polymer 202 disposed thereon. The electricallyconductive polymer 202 forms electrical contact to surface 204 ofsubstrate 200 along at least part of the interface 106 between theelectrically conductive polymer 202 and surface 204. The pattern 102 canelectrically interconnect a number of electronic devices formed insubstrate 100.

FIG. 2 shows schematically a side view of a substrate 208 having adielectric layer 210 on surface 212 of substrate 208. Dielectric layer210 has a through-hole 214 therein with patterned electricallyconductive polymer 216 disposed on dielectric layer 110 to fillthrough-hole 114 to contact surface 118 of substrate 108. Some examplesof devices useful to practice the present invention are liquid crystaldisplays (LCD), transistors (bipolar and field effect transistors),light emitting diodes, etc.

LCD Devices

Liquid crystal based electro-optical transducers are currently the stateof the art technology for the manufacture of flat panel displays inparticular for portable electronic equipment. It is expected that thistechnology will continue to dominate in the future as the industry movestowards large area displays.

A typical liquid crystal (twisted nematic) cell is shown in FIG. 3. Inthis device the nematic liquid crystal is placed between two glassplates which are on average 5-20 &mu.m apart. On the surface of theglass plates is deposited the transparent electrode, indium tin oxide(ITO). On the ITO is deposited an alignment layer which is rubbed insuch a way that the nematic liquid crystal aligns parallel to the rubbeddirection. If the two alignment layers are rubbed at 90 &deg. angles toone another the liquid crystal adapts a twisted structure as is shown inFIG. 4 a. If polarized light is incident on the cell, the plane ofpolarization will follow the twist of the molecules and thus, will berotated by 90 &deg. as it passes through the cell. If a second polarizerplaced at the other end of the cell is also rotated 90 &deg. relative tothe first polarizer, the light will pass through the cell. When avoltage is applied to the cell an electric field is in turn appliedacross the liquid crystal cell. The liquid crystal molecules alignthemselves with the electric field (FIG. 4 b) which results indisruption of the twist. The incident light now sees cross polarizersand, therefore, there is no light transmission through the cell. U.S.Pat. No. 5,623,514 describe liquid crystal cells, the teaching of whichis incorporated herein by reference.

There are a variety of liquid crystal displays including passive andactive matrix displays. Active matrix displays can consist of twoterminal devices such as diode rings, back to back diodes andmetal-insulator-metal device. Active matrix displays can also consist ofthree terminal devices such as thin film transistors where the materialis polysilicon, amorphous silicon, amorphous germanium, cadmiumselenide, etc.

Another technology that is under tremendous research and development forpotential future use in flat panel displays is light emitting diodes, inparticular where the electroluminescent layer is an organic material.Light emitting diodes consist of an injecting electrode, anelectroluminescent layer, and an electron injecting electrode. The holeinjecting electrode is most commonly indium tin oxide.

Today, flat panel displays are predominantly manufactured using thinfilm transistor based active matrix liquid crystals. One of the mostcumbersome process steps in liquid crystal cells is the deposition andpatterning of the ITO electrode. The ITO is first deposited by anevaporative process. It must then be annealed at high temperatures forseveral hours. The ITO is then patterned by applying a photoresist. Thephotoresist is exposed and developed. The pattern is transferred to theITO by etching. The etching solution consists of a mixture of strongacids. ITO is generally deposited either before or after the thin filmtransistor layers have been deposited. In the latter case, the ITOacidic etching solution can cause defects in the thin film transistordevices.

It is therefore desirable to develop new electrode materials that offera simple approach as compared to ITO but at the same time offer highoptical transmission, good conductivity, good environmental and thermalstability, ease of patterning by lithography, and good liquid crystaldisplay properties such as high charge retention, low image sticking,and good transmission/voltage characteristics. It is also desirable todevelop improved electrode materials and electrical contacts for lightemitting diodes and other devices.

Electrically conducting polymers are a relatively new class ofelectronic materials that may be considered as potential candidates forelectrode materials. These polymers have the potential of combining theelectrical properties of metals with the processing advantages ofconventional polymers. Herein we describe substituted and unsubstitutedelectrically conducting polyanilines, polyparaphenylenes, polyazines,polyparapheylenevinylenes, polythiophenes, polyfurans, polypyrroles,polyselenophenes, polyisothianapthenes, polyphenylene sulfides,polyacetylenes, polypyridylvinylenes, combinations thereof and blendsthereof with other polymers and copolymers of the monomers thereof.

In order for these polymers to be used as an ITO alternative or as anelectrode general they must have suitable conductivity, be easilypatternable and in certain cases have high optical transmission. Inaddition, these polymers cannot outgas as they would cause contaminationof devices. In a liquid crystal display cell, outgassing by theconducting polymer would significantly reduce the charge retention ofthe display. Furthermore, the conducting polymers need to be easilypatternable by lithography. Patterning cannot result in a decrease inthe conductivity of the conducting polymer nor cause any deteriorationof the properties of the conducting polymer. It is therefore desirableto develop a method of patterning these polymers, ideally a method thatcan be used on any conducting polymer system and does not negativelyimpact the properties of the conducting polymer.

One potential conducting polymer that can be used as a conductingelectrode is polyaniline. Polyaniline (and other conductive polymers) isa family of polymers as described in U.S. Pat. No. 5,198,153, U.S. Pat.No. 5,200,112 and U.S. Pat. No. 5,202,061 entitled, “ElectricallyConductive Polymeric Materials and Uses Thereof” incorporated herein byreference.

In order for a conductive polymer, such as polyaniline to be consideredas a conducting electrode in for example liquid crystal displays, it isdesirable that the polymer exhibits certain properties. By way ofexample, the present invention will be described with reference topolyaniline, but the invention is not limited thereto. These include:

1. It preferably exhibits an optical transmission greater than 80% inthe visible range while still exhibiting sufficient conductivity andcontact resistance to the device metallurgy.

2. It preferably exhibits good solubility and forms uniform coatings.Coatings preferably do not contain particles, streaks, or significantpinholes or dewets.

3. It preferably is compatible with the alignment layer that isdeposited on top of the conducting electrode; the solvents used todeposit the alignment layer which in most cases is polyimide should notdissolve the polyaniline, cause significant interfacial mixing, orextract any of the dopant ions from the polyaniline. Extraction of thedopant ions would result in a decrease in conductivity of polyanilineand the dopant ions could potentially go into the alignment layer andultimately in the liquid crystal thereby destroying the properties ofthe liquid crystal cell;

4. It is preferred that the polymer exhibits thermal stability at leastto 150° C.;

5. It is preferred that the polymer does not exhibit outgassing as anyoutgassing would result in ionic contaminates going into the liquidcrystal and this would destroy the characteristics of the liquid crystalcell;

6. It is preferred that the polymer provides good step coverage;

7. It is preferred that the polymer be patterned without the need ofharsh etchants;

In addition to the polymer properties described above, it is alsoimportant that the liquid crystal cells made with the polyanilinepreferably exhibit certain properties. These include:

1. Good Transmission vs. Voltage Characteristics;

2. Good Charge Retention at room temperature and at elevatedtemperature;

3. No image sticking either at room temperature nor at elevatedtemperature.

It is not obvious that a conductive polymer, such as polyaniline, can beused for such an application and result in the properties outlinedabove. It is known that polyaniline is made conducting by reacting thenon-conducting form of the polymer (the base) with acids such ashydrochloric acid to result in a conducting salt. This is described inFarad. Discuss. Chem. Soc., 88, 317, by A. G. MacDiarmid and A. J.Epstein. The structure for the conducting form consists of delocalizedpolymeric radical cations that are neutralized by counteranions aredescribed in U.S. patent application Ser. No. 08/370,127 filed on Jan.9, 1995 entitled, “Deaggregated Electrically Conductive Polymers andPrecursors Thereof” incorporated herein by reference below.

Ions are necessary to render the material conducting. It is well knownthat the presence of ions in liquid crystal panels will result in poorcharge retention and poor image sticking as shown in H. Seiberle, M.Schadt, “Influence of Charge Carriers and Display Parameters on thePerformance of Passively and Active Addressed LCDs”, SID '92 Digest, 25(1992). This is one of the biggest concerns using polyaniline as anelectrode. The use of HCl acid as a dopant results in volatile, mobileions. It is actually observed that HCl outgasses from thin films ofpolyaniline at temperatures as low as 40-50° C. This outgassing woulddestroy the properties of the liquid crystal (LC) as the ions wouldmigrate into the LC. Herein, we find quite surprisingly that thepolyaniline can be modified to result in a doped polymer that does notresult in ion migration into the LC at room temperature nor at elevatedtemperatures and as a result LCDs are made with excellent chargeretention and image sticking properties.

Another concern with the ions is that during the deposition of thepolyimide alignment layer on top of the polyaniline electrode, thesolvent used for the polyimide which generally is a highly polar solventsuch as NMP or gamma-butyrolactone, both quite polar solvents, wouldextract the dopant ions from the polyaniline and have these ions in turnmigrate into the alignment layer and into the LC. This again woulddestroy the properties of the display. In addition, extraction of theions would result in a decrease in conductivity of the polyaniline.Quite surprisingly, it is found that the polyimide alignment layerproves quite compatible with the polyaniline and extraction of the ionsdoes not occur.

Polyaniline preferably provides good optical transmission whileexhibiting sufficient surface resistance and contact resistance to thedata metal line beneath. One can tailor optical transmission of thepolyaniline by reducing the thickness but while doing this the surfaceresistance of the material increases. Herein we describe a material thatexhibits good optical transmission, good surface resistance and goodcontact resistance to metal.

Polyaniline preferably provides good step coverage. This is a majorproblem when using ITO. In a typical TFT configuration, Indium tin oxide(ITO) is used as the transparent conducting electrode. The ITO isdeposited by sputtering and lithographically patterned by a conventionalphotoresist system. Then it is etched using a hot solution of a mixtureof concentrated nitric and hydrochloric acids. Generally, the ITO isdeposited either before or after the thin film transistor (OFF) layersand passivation layer have been deposited. To reduce the number ofphotolithography mask steps, the latter case is used. In this case, viaholes in the passivation layer are formed to provide connection for theITO layer to the underneath source/drain metal of TFT devices. If thepassivation layer is too thick, the ITO has a step coverage problem tothe via hole since ITO is deposited by a sputtering process. On theother hand, when the passivation layer is thin, pin holes are generallypresent and the ITO acidic etching solution can cause defects in the TFTdevices or in the bus lines. Polyaniline would be deposited by aspin-coat or roller coat process. It would therefore be able to providegood step coverage. Polyaniline is also found to be patterned withoutthe need of harsh etchants.

Although this invention is suitable for a number of devices, it will bedescribed in embodiments of an active liquid crystal display andspecifically for a thin film transistor (TFT) liquid crystal display. Asshown in FIG. 5, a conventional TFT display 10 comprises an array ofcells or A, each cell including a thin film transistor 11 to address thecell by applying a voltage to the cell when the transistor is in its onstate and a capacitor 12 which maintains the voltage after thetransistor is switched off. The transistor is formed on a glasssubstrate 13 on the back side of the display 10 and is connected betweena column data electrode 14 and a row electrode 15 and to a displaytransparent electrode 16 of each pixel, all at the back side of thedisplay 10. The front side of the display is formed with a continuouscommon transparent electrode 17 which is spaced apart from andpositioned parallel to the transparent display electrode 16. Both theelectrode 17 and the display electrode 16 are preferably formed of athin transparent conductive material, such as indium tin oxide (ITO),carried on a glass substrate. Since the display electrode 16 of eachpixel is smaller in dimension then the continuous common electrode 17, afringe field results which spreads outward from the pixel or cell edgesof the display electrode to the common electrode when voltage is appliedacross the electrodes. Parallel with the outside of the common electrode17 and adjacent to the glass substrate 18 is a polarizer 19, which isappropriately oriented relative to the a polarizer 20 mounted in back ofthe rear glass substrate 13. Alignment layers 21 and 22 are disposed onthe inner surface of the display and common electrodes 16 and 17,respectively, and are in contact with a liquid crystal layer hereintwisted nematic liquid crystal molecules which is sealed between the twoparallel mounted glass substrates 1 and 18 carrying the alignment layers21 and 22. On the back side of the display a visible light source (notshown) which irradiates the display 10 through a diffuser If it isdesired to have the display 10 in color, a color filter 25 is disposedon the alignment layer side of the common electrode 17, and containsgroups of the three primary colors (red, green and blue), each one ofthe primary colors being associated with one of a group of threeadjacent pixels A to form a color cell.

Liquid crystal cells were fabricated in which patterned electricallyconducting polymers (i.e. polyaniline) functioned as the transparentelectrode 16 of each pixel element in the display 10 above ITO functionsas the continuous transparent electrode 17. In addition, liquid crystalcells were fabricated in which patterned electrically conductingpolymers act as the transparent electrode 16 and continuous coatings ofelectrically conducting polymers act as the continuous transparentelectrode 17. Electrically conducting polymers also act as thetransparent conducting electrode 17 and patterned ITO can act as thepixel electrode 16.

FIG. 6 shows a top view of a unit cell structure of a TFT/LCD display.101 and 102 are the data bus lines and 103 and 104 are gate bus lines.106, 107 and 108 form a thin film transistor (TFT), in which 108 is aprotrusion of 104 and 106 is a protrusion of 101. 106 is the sourceelectrode and 107 is the drain electrode. 106 and 107 are typically madeof the same electrically conductive material such as metal. 105 is atransparent pixel electrode which is made of a conductive polymer by aphotolithograph. Pixel electrode 105, top electrode on the color filterside (not shown) and the liquid crystal (not shown) between these twoform a pixel capacitor. 130 is an extension of 105. 130 and 103 areseparated by a layer of insulator (not shown) and form a storagecapacitor. When an appropriate high voltage is applied to the gate busline 104, the TFT is turned on. Therefore, the pixel capacitor and thestorage capacitor are charged from data bus line 101 through the TFT tothe designed voltage which determines the electro-optics of the liquidcrystal in the pixel. Thus, the designed image is displayed. Twocross-sectional structures along the A-A′ are shown on FIGS. 7 and 8. InFIGS. 7 and 8, 106 is the source electrode, 107 is the drain electrode,108 is the gate electrode, 109 is the gate insulator layer, 110 is theamorphous silicon layer, 111 is the n+amorphous silicon layer, 112 isthe passivation layer, 105 is the pixel electrode. In FIG. 8, on top ofthe passivation layer 112, there is another layer 113, which is a lowdielectric transparent polymer layer. The pixel electrode layer 105 isplaced on top of 113 so that the pixel electrode can be extended to thetop of the data bus line to increase the pixel aperture ratio. In FIG.7, pixel electrode 105 and 107 have a direct overlap. In FIG. 8, thisoverlap is through a via hole on the polymer layer 113. FIG. 9 showspart of the assembled liquid crystal display. 120 is the glasssubstrate. 121 is the color filter layer. 122 is the conductivetransparent electrode layer. 122 can be an indium tin oxide (ITO) layeror a transparent conductive polymer layer. 123 is a transfer pad whichis connected to an electrode leaf (not shown) for tab bonding to drivingelectronics. 123 is made of metal layer. 124 is the conductive epoxywhich electrically connects 122 and 123. Thus, 122 can be connected to adriving electronics through 124 and 123. 125 is a liquid crystal layer.All metal layers and electrically conductive layers in FIGS. 6-9 can bereplaced by the electrically conductive polymers according to thepresent invention.

Thin Film Transistor Devices

The electrical contacts or electrodes in current thin film transistors(TFT) devices are metals. Metals deposited by an evaporative orsputtering process which requires expensive tooling.

Suitable polymers include substituted and unsubstituted electricallyconducting polyaniline polyparaphenylenes, polyparapheylenevinylenes,polythiophenes, polyfurans, polypyrroles polyselenophenes,polyisothianapthenes, polyphenylene sulfides, polyacetylenes, polyazinespolypyridylvinylenes, combinations thereof and blends thereof with otherpolymers copolymers of the monomers thereof.

In order for these polymers to be used as a contact electrode in TFTthey preferably have suitable electrical conductivity and be easilypatternable. In addition, these polymers cannot outgas causingcontamination of devices. Furthermore, the conducting polymerspreferably are patternable by lithography. Patterning preferably doesnot result in a decrease in the conductivity polymer nor cause anydeterioration of the properties of the conducting polymer.

It is therefore desirable to develop a method of patterning thesepolymers, ideally a method that can be used on any conducting polymersystem and does not negatively impact properties of the conductingpolymer.

The use of a conducting polymer electrode as at least one of the sourceand the drain in a TFT having a different-type conjugated polymer as thesemiconductor layer has been described earlier (H. Koezuka, A. Tsumura,T. Ando, U.S. Pat. No. 5,107,308). In this patent the gate consistentlycomprised of a metal. Furthermore, whenever one of the drain electrodesin a TFT was a film of a conducting polymer, this film had a patternedmetal lead. The method used for the growth of the conducting polymer waselectrochemical polymerization. Although the authors of the above patentgenerally describe a different method can be used to form the conductingpolymer electrode, they do not offer any solution to the problem of howto pattern the conducting polymer layer to the required shape of thesource and/or the drain electrodes and form the transistor channelbetween the electrodes. In the present patent application we presentdevices that use conducting polymer one or more of the source, the drainand the gate electrodes of a TFT and ways to pattern a conductingpolymer layer.

The present invention is also directed to TFT devices, in which one ormore of the source, drain and gate electrodes comprise an electricallyconducting polymer. FIGS. 10 to 13 show configurations of TFT devices.

FIG. 10 shows a device made on a substrate 61. A patterned conductingpolymer gate electrode 62 is disposed on the substrate 61. An insulatinglayer 63 is disposed on top of the gate electrode 62. Source 65 anddrain 66 electrodes comprising a conducting polymer were disposed andpatterned on top of the gate insulator 63. The semiconductor layer 64 isdisposed over the source 65 and the drain 66 electrodes and part of thegate insulator 63.

FIG. 11 differs from FIG. 10 in that the substrate 61 is conductive andacts as the gate 61. A specific but not limiting example of thisstructure is to have a heavily doped wafer as substrate/gate electrode(61 and 62) and use a thermally grown oxide 63 as insulator on top ofit. The rest of the layers remain as described in FIG. 10.

FIG. 12 differs from FIG. 10 in that the source 65 and drain 66electrodes are disposed on top of the semiconductor layer 64, which wasearlier disposed on the gate insulator.

FIG. 13 differs from FIG. 11 in that the source 65 and drain 66electrodes are dispose on top of the semiconductor layer 64, which wasearlier disposed on the gate insulator.

FIG. 14 shows a plot of the current flowing between the source and thedrain of the TFT device, whose structure is schematically drawn in FIG.11, versus the voltage gate electrode. The channel length, L, of thisdevice was 100 microns and the channel width was 1500 microns.

FIG. 15 shows the top view of a typical layout of a TFT based activematrix liquid crystal display. One or more of the source, the drain, andthe gate electrodes comprise polymer.

FIG. 16 shows cross sections of a pixel of a TFT based active matrixliquid crystal cell having two different TFT configurations, FIG. 16(a)and FIG. 16(b). One or more of the source, the drain, and the comprise aconducting polymer.

FIG. 17 shows contact via through a passivating or insulating layer. Thebottom a conducting polymer. The top layer could be either the same or adifferent conductive material such as a metal, conductive polymer orITO.

Led Devices

Patterned electrically conductive polymers are also useful to fabricateelectroluminescent diodes. More particularly, this invention relates toa transparent cathode and anode structure for light emitting diodes(including organic light emitting diodes) which, when fabricated ontransparent substrates, renders a display which is at least partiallytransparent and when fabricated on an opaque substrate containingdevices and circuits renders a display viewable from the cathode side.The present invention applies to LEDs having an organic and an inorganicelectroluminescent region. The invention will be described withreference to OLEDs but is not. limited thereto.

Organic light emitting diodes (OLEDs) described in prior work werefabricated on glass substrates, and their lower electrode was thetransparent conductor indium tin oxide (ITO). The top electrode forthese devices was opaque so that light from the electroluminescentregion could be viewed only from the glass side. One exception is thestructure recently reported by V. Bulovic et al. in Nature 380, 29(1996) in which the cathode metal is thinned during the subsequent ITOdeposition and made partially transparent.

An OLED display on an opaque substrate or a transparent OLED display ona transparent substrate requires a top electrode structure thatsatisfies the following criteria to (1) be transparent to the LEDemission, (2) provide a low series resistance current injection into theLED active region, (3) provide, sufficiently high lateral conductivityon the plane of the electrode when these diodes are formed intotwo-dimensional arrays self-emissive displays, (4) act as a protectivefilm to the chemically and physically delicate underlying organic film,and (5) be able to be deposited in a benign fashion without damaging theorganic layer on which it is deposited so that the integrity of thelayer/electrode interface is preserved. The common transparent electrodematerial is indium tin oxide (ITO), often used as an anode in OLEDs,satisfies requirements 1-4, but it is typically deposited in an oxygenplasma ambient that causes damage to the organic region in the OLEDdevice structure and therefore does not satisfy (5). The same is truefor GaN as an electrode. Criterion (5) is actually the most crucialsince, although there are several transparent conductive materials,nearly all involve plasmas or high processing temperatures whichirreversibly damage the organic light emitting material.

What is needed is a transparent cathode and/or anode structure that isconvenient to make and satisfies all of the above requirements.

It is therefore desirable to develop new electrode materials that offera simpler process than ITO but at the same time offer high opticaltransmission, good conductivity environmental and thermal stability, andease of patterning by lithography.

A typical light emitting diode configuration consists of a holeinjecting electrode, an electroluminescent layer and an electroninjecting electrode. This is the basic configuration. Sometimes holetransport layers can be incorporated between the injecting electrode andthe electroluminescent layer to enhance the mobility of the holes and toisolate the holes. Also, an electron transport layer can be includedbetween electroluminescent layer and the electron injecting electrode.

The electroluminescent layer can be an organic conjugated polymer, anorganic small molecule such as the AlQ materials or it can be aninorganic material such gallium arsenide. Typical hole injectingelectrodes include ITO. Typical electron injecting electrodes includealuminum, calcium, etc.

P-doped electrically conductive polymers according to the presentinvention can be used as hole injection layers and M-doped electricallyconductive polymers according to the present invention can be used aselectron injection layers.

An example of the structure of a prior art OLED 300 is shown in FIG. 18.The substrate 312 is glass, and an ITO film 314 is deposited directly onthe glass and to form an anode. For efficient operation the organicregion commonly consists of layers and shown in FIG. 18 are a holeinjection layer 316, a hole transport layer 318 and electroluminescent(EL) layer 320. EL layer 320 is the metal chelatetris(8-hydroxyquinoline) aluminum, (sometimes abbreviate S or Alq3). Thehole transport layer in this configuration is an aromatic diamine. Themetal alloy MgAg is deposited on top of the organics to form a cathode322 which is opaque for thicknesses greater than approximately 10 nm.Not shown is a hermetic seal that is sometime used to protect thecathode from moisture.

The EL layer in the structure of FIG. 18 is a member of the class oforganic materials known as molecular organics. These are seriallydeposited by an evaporation process. Polymers form another class oforganic materials exhibiting electroluminescence and are usually appliedby spin coating. Polymer OLEDs are also commonly made on glasssubstrates using an ITO anode and have an opaque cathode (usually a lowwork function metal such as calcium) so that light is emitted from oneside only. They may also employ multiple polymer layers to improveoperating efficiency.

An exemplary embodiment of the LED of this invention is an OLED having atransparent cathode 340 which is depicted by the general structure inFIG. 19. If the OLED is formed on a glass substrate 332 or plasticsubstrate with an ITO (or electrically conductive polymer) anode 334,light is now emitted from both sides, and the OLED is at least partiallytransparent. A viewer looking at a display consisting of an array ofsuch OLEDs could either focus on the image presented on the display orcould look through the display at the scene beyond. On the other hand adisplay formed on an opaque substrate, such as silicon, and using OLEDswith a transparent cathode could be viewed by looking at the lightemitted from the cathode side. Fabricating an OLED display on silicon isadvantageous because the devices and circuits can be formed in thesilicon prior to depositing the. OLED on the silicon, and the devicesand circuits can be used to make an active matrix display with integratedrivers.

According to the present invention the anode or cathode of the LED canbe formed from or covered by a protective layer of an abrasion andscratch resistant electrically conductive polymer as incorporated byreference herein. Light emission from an OLED having the cross sectionshown in FIG. 19 is from both the top and the bottom (i.e., from bothsides of the diode) since both anode and cathode are transparent.

The electrically conductive polymers described herein provide asatisfactory cathode electrode by meeting the requirements oftransparency, perpendicular conduction for low series resistance,formation of a protective film and a damage free deposition process.Abrasion and scratch resistant electrically conductive polymers aredescribed in U.S. patent application Ser. No. 08/193,926 filed Feb. 9,1994 and U.S. patent application Ser. No. 08/476,141 filed Jun. 7, 1995both entitled, “Electrically Conductive and Abrasion/Scratch ResistantPolymeric Materials, Method of Fabrication and Uses Thereof”, theteaching of which is incorporated herein by reference. Below eachrequirement is considered individually.

A display device is formed by fabricating many identical OLEDs on amonolithic substrate arranged into a two-dimensional array and providingthe means of controlling the light emission from each diode. Generally,the image is formed a line at a FIG. 20A (passive matrix approach), forexample, the selected row line 490 is brought to a positive voltage Vrwhile all unselected row lines 492 remain at ground. A voltage isapplied to each column line 494, 496 where i is the column line indexand runs fro the maximum number of column lines. The forward bias onOLEDs 498, 400 along the selected row line 490 is then Vr−Vci and thisvoltage determines the amount of emitted. All other OLEDs 402, 404 arereverse biased and emit no light.

For the array shown in FIG. 20A, an OLED emits light only when its rowline accessed and this can produce flicker in high information contentdisplays. This is remedied by the array shown in FIG. 20B (active matrixapproach) where a circuit included at each cross point is used to samplethe column line voltage and hold the other row lines are accessed. Inthis case all diodes share a common cathode. Because these circuits needto be small and fast, it is convenient to fabricate single crystalsilicon. In this second case, the substrate is opaque and a transparentcathode is required to view the image.

References cited herein are hereby incorporated herein by reference.U.S. patent application Ser. No. 08/794,072 filed on Feb. 4, 1997assigned to the assignee of the present invention describes OLEDstructures and methods of fabrication, the teaching of which isincorporated herein by reference.

Methods of Patterning

To be able to be used as a electrode or electrical contact, theelectrically conducting polymer is preferably patterned. A number ofmethods are described herein which can be used to pattern the variouselectrically conductive polymers.

These include an application of a resist material to the surface of theconducting polymer. The resist can be negative or positive type and canbe developed in aqueous or organic solvents. Examples of negativeresists are polymethylnethacrylate type, novolak/diazonaphthaquinonesystems, t-boc protected styrene polymers and copolymers thereof,t-butyl protected styrene polymers and copolymers thereof, t-butylprotected styrene polymers and copolymers thereof, other acid liabledeprotected acrylate ester polymers and copolymers thereof. These areexemplary only and not limiting. Examples of positive resists are epolycontaining polymers, hydroxystyrenr polymers with cross-linkers, andsiloxane polymers. These are exemplary only and not limiting. The resistis exposed to a given radiation, such as ultra-violet/visibleelectron-beam x-ray and ion beam aqueous tetramethyl ammonium hydroxideaqueous tetramethyl amonium hydroxide, aqueos NaOH, aqeous KOH,methylisobutyl ketone. aqueous tetraethylammonium hydroxide, isoprpanol,propylene, glycole methyl ether acetate, diglyme, methyl ethyl ketoneand These are exemplary only and not limiting. The resist image issubsequently transferred to the conductive polymer by reactive ionetching (RIE) such as with oxygen gas, Co₂, SO₂, fluorine, etc. Once theimage is transferred to the conducting polymer, the remaining resist isremoved, preferably by a solvent wash acetone, diglyme, isopropanol,etc. This scheme is outlined in FIG. 21. It is desirable that thesolvent used to apply the resist as well as the developer of the resistand conditions under which the resist is developed, and the solventwhich is used to remove the resist, does not result in the deteriorationof the conducting polymer's properties such as the conductivity, otransmission, thermal stability, and so on.

A second method of patterning the conducting polymer is with thedeposition of a metal such as aluminum, gold, etc. on the surface of theconducting polymer. A patterned metal layer is deposited on theconducting polymer by depositing the metal through a metal mask Thepattern is then transferred to the conducting polymer by etching such asby oxygen gas CO₂, SO₂, fluorine, etc. RIE. The metal is then removed byetching with an acid solution such as hydrochloric acid, hydrofloricacid, acitic acid, sulfuric acid, perchloric acid, phosphoric acid,nitric acid and any combinations thereof. This scheme is depicted inFIG. 22. It is desirable that the conditions under which the metal isdeposited and etched does negatively impact the properties of theconducting polymer.

A third method of patterning the conducting polymer is with thedeposition of blanket metal, such as aluminum, gold, etc. on the surfaceof the conducting polymer. The metal is patterned by the application ofa resist. A, the resist is exposed to radiation, such as ultra-violet,visible, electron beam, x-ray, ion-beam and developed, using similardevelopers described above, the pattern is transferred to the metallayer by etching the metal, for example, with an acid solution such asdescribed above. The pattern then transferred to the conducting polymer,for example. by oxygen, CO₂, SO₂, fluorine, etc. reactive ion etching.This is followed by removal of the resist by a solvent followed byremoval of the metal by an acid etch, similar to these described above.This scheme is illustrated in FIG. 23. It is desirable that of the aboveprocessing steps and solvents used in these steps do not adverselyaffect properties of the conducting polymer.

A fourth method of patterning the conducting polymer is by directexposure to radiation. The conducting polymer is radiation sensitive andresults in a solubility difference between exposed and unexposed regionsupon irradiation. The radiation can be electron beam, ion beam, andelectromagnetic radiation (for example, x-rays and light). In this casethe more soluble region exposure are removed by a solvent wash thusresulting in direct conducting polymer patterns. This scheme is depictedin FIG. 24 and as described in U.S. Pat. No. 5,198,153, the teaching ofwhich is incorporated herein by reference.

In all of the above cases, the exposure to radiation can includeelectromagnetic radiation, such as x-rays, and light of variouswavelengths and include charged uncharged particle beams such aselectron beams, iion beams, and elementary particle beams.

Specific Examples Follow:

1. Polyaniline doped with acrylamidopropanesulfonic acid described inU.S. application Ser. No. 08/595,853 filed on Feb. 2, 1996, the teachingof which is incorporated herein by reference was spin applied on to aglass substrate from a suitable solution includingN-methylpyrrolidinone, m-cresol, dimethylpropylene urea, dimethylsulfodimethylformamide, etc. The thickness of the coating can be controlledby the concentration of the polymer in solution as well as by the spinspeed. Generally a 0.1% to 5% solution was utilized of the polymer in agiven solvent. The thickness of the coating ranged from 500 to 1000Angstroms. The conductivity of the film ranged from 1 to 150 S/cm. Thecoated film was baked in an oven at 85° C. for 5 minutes to removeresidual solvent. On to this polyaniline surface was applied aconventional Shipley photoresist (MP 1808). The resist is baked at 85°C. for 30 minutes The resist coated polyaniline substrate was thenexposedto ultra-violet light at a dose of 70 mj. The resist wassubsequently developed in an aqueous alkaline Micropos CD-30 developer.As the developer which is alkaline can dedope the polyaniline and renderthe polyaniline less conducting, it is desirable that the developer andtime of development be closely controlled. In this case, the developerconcentrate is diluted with deionized water by 50%. The resist wasdeveloped for 30 seconds followed by a rinse with water. The developedresist is then cured at 100° C. for 30 minutes to harden the resistprior to image transfer. The resist image was then transferred to thepolyaniline by oxygen reactive ion etching. The polyaniline was etchedusing 150 watts RF power load, 100 mtorr pressure and 20 sccm of oxygengas in a reactive ion etching chamber for 2 minutes. After the image wastransferred, the remaining photoresist was removed by washing withacetone. 10 &mu.m conducting polyaniline lines imaged in this fashionare shown FIGS. 25 and 26. The conductivity of the polyaniline patternswas measured and found to be similar to the starting conductivity. Inother words, no significant decrease in conductivity is attained as aresult of this process. Other properties including the opticaltransmission and thermal stability and overall environment chemicalstability were also evaluated and are discussed below.

2. Poly(3-butylthiophene-2,5-diyl) was dissolved in a suitable solventsuch as tetrahydrofuran, methyl ethyl ketone, N-methyl pyrrolidinone,etc and spin coated on a glass plate. The polythiophene was then dopedby exposing the film to a chamber of iodine. The doped sample was thenpumped under dynamic vacuum. A conductivity of 1000 to 2000 S/cm wasattained. This film was patterned by applying the Shipley photoresist MP1808 as described above for the polyaniline.

3. Poly(3-hexylthiophene-2,5 diyl) was also dissolved. coated, and dopedin the manner stated above and patterned as described in example 1.

4. Poly(3-octylthiophene-2,5 diyl) was treated and patterned asdescribed above.

5. Polypyrrole was deposited on a glass plate as follows. Pyrrolemonomer (0.045M) was dissolved in 500 ml of water. In a second beakerwas dissolved the oxidant FeCl₃ (0.105M) in 500 ml of water. (0.105M) of5-sulfosalicyclic acid and (0.105M) of anthraquinone-2-sulfonic acidsodium salt are then added to the oxidant solution. A glass plate whichhad one side masked was dipped into the monomer solution. The oxidantsolution is then added to the monomer solution. The solution is allowedto reach for 10 to 30 minutes to allow the polymerization of the monomerto proceed and deposit on the glass plate. The thickness of theconducting polypyrrole that deposits on the glass plate depends on thetime the glass plate is allowed to sit in the polymerization bath. Thepolypyrrole had conductivity on the order of 200 S/cm. The polypyrroledeposited on the glass plate was then patterned by applying a resist asdescribed above.

6. Polyaniline doped with acrylamidopropanesulfonic acid wasspin-applied on to glass plate. 300 Angstroms of blanket aluminum wasevaporated on the polyaniline 2.0 &mu.m thick of a Shipley polypropyleneglycol ether acetate solvent based resist was applied on the aluminum.The resist was exposed to ultra-violet light at a dose 150 mj andsubsequently developed with a 50/50 mixture of Microposit developerconcentrate and deionized water. After developing, the resist is bakedat 85° C. for 30 minutes. The pattern is then transferred to thealuminum by etching the aluminum at room temperature using Transenealuminum etch solution consisting of 80% phosphoric acid, 5% aceticacid, 5% nitric acid, and 10% water. The etch rate w 4.19 Angstroms/sec.The pattern is in turn is transferred to the polyaniline by oxygenreactive ion etching using 20 sccm of oxygen at 100 mtorr pressure and150 watts power load at an etch rate of 39 Angstroms/sec. An alternativemethod to transferring the pattern to the polyaniline is to carry outthe aluminum etch at 30° C. At elevated temperature, both the aluminumand the polyaniline are etched by the acid solution at a rate of 37Angstroms/sec. The remaining resist is removed by an acetone rinse. Theremaining aluminum is etched away using a dilute 25% dilute hydrochloricacid solution. FIGS. 27, 28, and 29 depict conducting polyanilinepatterned in this fashion.

7. The substituted polythiophenes and in-situ polymerized polypyrroledescribed were also patterned using aluminum blanket metal as describedfor the polyaniline above.

8. Polyaniline acrylamidopropanesulfonic acid was deposited onto a glassslide. On this surface was deposited a pattern of aluminum lines througha metal mask. The pattern was transferred to the polyaniline by oxygenreactive ion etching. The remainder of the aluminum is then etched witha dilute hydrochloric acid solution. This method is ideal for relativelylarge features. 50 μm polyaniline lines were fabricated in this fashionas is shown in FIGS. 30 and 31.

9. The substituted polythiophenes and in-situ polymerized polypyrrolescan also be patterned in this fashion.

10. The polyaniline acrylamidopropanesulfonic acid can be patterneddirectly by exposing the film to radiation such as electron beam. Uponirradiation, the polymer undergoes cross-linking and becomes insoluble.The unexposed regions are removed with a solvent wash to result inpatterns of conducting polyanilines.

The conducting polymer can be spin-applied, dip coated, roller coated,spray coated on to a substrate or it can be in-situ chemically orelectrochemically polymerized a surface.

In order for the conducting polymer to be used in liquid crystaldisplays the optical transmission of the film is preferably in excess of80% in the visible range. FIG. 32 depicts the optical transmission ofthe polyaniline acrylamidopropanesulfonic acid (blanket and patternedlines). As can be seen the polymer as a 500 Angstrom film exhibitsgreater than 90% transmission throughout the visible range. This matchesthe optical transmission that is typical of annealed indium tin oxide.The conductivity of the polyaniline lines was on the order of 100 S/cmand is preferably greater than 100 S/cm. The material exhibitedenvironmental stability in that there was no change in conductivity overtime in air. The material is thermally stable to about 150 &deg.C.

As the properties of the material looked good, liquid crystal cells wereassembled in which a conductive polymer such as polyaniline was used asboth electrodes as well as cells in which the polyaniline was used asone electrode while indium tin oxide is used as the second electrode. Inthe case where polyaniline was used as both electrodes, one of theelectrodes consisted of patterned lines whereas the second electrodeconsisted of a blanket film. On the polyaniline was spin-coated thealignment layer which was polyimide (Nissan SE5210). The polyimide wascured at 125 &deg. for 1 hour. The thickness of the film was 500Angstroms. The polyimide layers were then mechanically rubbed. The testcell was filled with a Merck liquid crystal containing a left chiralagent. Polarizers were attached to the outside of the glass withtransmissive axis of the polarizer parallel to the rubbing directions.Thus, a right handed 90 &degree twisted nematic test panels werecompleted. The performance of the liquid crystal cells was thenmeasured. FIG. 33 depicts the transmission/characteristics for theliquid crystal cell consisting of the two polyaniline electrodes. Thismatches the transmission/voltage characteristics exhibited by crystalsconsisting of indium tin oxide electrodes (FIG. 34). The chargeretention of the liquid crystal containing polyaniline electrodes was95% at room temperature (FIG. 35). Again this matches the chargeretention exhibited by liquid crystal cells consisting of ITOelectrodes. Image sticking of the liquid crystal cells were also in goodagreement.

FIG. 41 shows a surface 411 of substrate 413 having a layer of material415 disposed thereon and a layer of material 417 disposed on surface 411in a manner so that material 417 overlaps material 415 in an overlapregion 419 Material 417 can be an electrically conductive polymeraccording to the present invention and material 415 can be anon-polymeric electrically conductive material, such as a metal or asemiconductor. Also, both regions 417 and 415 can be electricallyconductive polymers.

FIG. 42 shows a surface 423 of substrate 421 having layers of material425 and 427 which abut at interface 429. Material 425 and 427 can beelectrically conductive polymers or one of the layers 425 and 427 can bean electrically conductive polymer and the other a non-polymericelectrically conductive material, such as a metal or a semiconductor.

Using the methods of patterning electrically conductive polymers taughtherein and using the methods of patterning nonpolymeric electricalconductors known in the art the structures of FIGS. 41 and 42 can bereadily made.

FIG. 43 schematically shows a bipolar transistor having a substrate 802,buried subcollector 804, lightly doped region 896, base region 808,emitter region 810, dielectric layer 812 and highly doped region 814 toreach to the subcollector region 804. The dielectric layer has opening816 for contact of the emitter, opening 818 for contact to the baseregion and opening 820 for contact to region 814 to contact thesubcollector 804. Patterned electrical conductors or electrodes 822, 824and 826 provide electrical contact to the emitter, base and collectorregions, respectively.

Electrodes 822, 824 and 826 can be formed from an electricallyconductive polymer according to the present invention. The electricallyconductive polymer forming an ohmic contact to the active device regions810, 808 and 814.

Examples of electrically conductive polymers that can be used topractice the present invention are of substituted and unsubstitutedpolyparaphenylenes, polyparaphenylevevinylenes, polyanilines,polyazines, polythiophenes, poly-p-phenylene sulfides, polyfuranes,polypyrroles, polyselenophenes, polyacetylenes formed from solubleprecursors and combinations thereof and copolymers of monomers thereof.The general formula for these polymers, structures fabricated therewithand methods of use thereof can be found in U.S. Pat. No. 5,198,153 toAngelopoulos et al. and in copending U.S. Application Ser. No.08/193,926 filed on Feb. 9, 1994 and in copending US Application Ser.No. 08/476,141 filed on Jun. 7, 1995, the teachings of which isincorporated herein by reference.

The polyaniline class of conducting polymers has been shown to be one ofthe most promising and most suited conducting polymers for a broad rangeof commercial applications. The polymer has excellent environmentalstability and offers a simple, one-step synthesis. A number of solublederivatives can be made. For example, we previously disclosed a newfamily of water soluble conducting polyanilines in U.S. Pat. No.5,370,825, the teaching of which is incorporated herein by reference.

The following U.S. patents describe resists useful to practice thepresent invention are incorporated herein by reference: 5,580,694,5,554,485, 5,545,509, 5,492,793, 5,401,614, 5,296,332, 5,240,812,5,071,730, 4,491,628, 5,585,220, 5,561,194, 5,547,812, 5,498,765,5,486,267,5,482,817, 5,464,726, 5,380,621, 5,374,500, 5,372,912,5,342,727, 5,304,457, 5,300,402, 5,278,010, 5,272,042, 5,266,444,5,198,153, 5,164,278, 5,102,772, 5,098,816, 5,059,512, 5,055,439,5,047,568, 5,045,431, 5,026,624, 5,019,481, 4,940,651, 4,939,070,4,931,379, 4,822,245, 4,800,152, 4,760,013, 4,551,418, 5,338,818,5,322,765, 5,250,395, 4,613,398, 4,552,833, 5,457,005, 5,422,223,5,338,818, 5,322,765, 5,312,717, 5,229,256, 5,286,599, 5,270,151,5,250,395, 5,238,773, 5,229,256, 5,229,251, 5,215,861, 5,204,226,5,115,095, 5,110,711, 5,059,512, 5,041,358, 5,023,164, 4,999,280,4,981,909, 4,908,298, 4,867,838, 4,816,112, 4,810,601, 4,808,511,4,782,008, 4,770,974, 4,693,960, 4,692,205, 4,665,006, 4,657,845,4,613,398, 4,603,195, 4,601,913, 4,599,243, 4,552,833, 4,507,331,4,493,855, 4,464,460, 4,430,153, 4,307,179, 4,307,178, 5,362,599,4,397,937, 5,567,569, 5,342,727, 5,294,680, 5,273,856, 4,980,264,4,942,108, 4,880,722, 4,853,315, 4,601,969, 4,568,631, 4,564,575,4,552,831, 4,522,911, 4,464,458, 4,409,319, 4,377,633, 4,339,522,4,259,430, 5,209,815, 4,211,834, 5,260,172, 5,258,264, 5,227,280,5,024,896, 4,904,564, 4,828,964, 4,745,045, 4,692,205, 4,606,998,4,600,683, 4,499,243, 4,567,132, 4,564,584, 4,562,091, 4,539,222,4,493,855, 4,456,675, 4,359,522, 4,289,573, 4,284,706, 4,238,559,4,224,361, 4,212,935, 4,204,009, 5,091,103, 5,124,927, 5,378,511,5,366,757, 4,590,094, 4,886,727, 5,268,260, 5,391,464, 5,115,090,5,114,826, 4,886,734, 4,568,601, 4,678,850, 4,543,319, 4,524,126,4,497,891, 4,414,314, 4,414,059, 4,398,001, 4,389,482, 4,379,826,4,379,833, 4,187,331.

While the present invention has been described with respect to preferredembodiments, numerous modifications, changes, and improvements willoccur to those skilled in the art without departing from the spirit andscope of the invention. All references cited herein are incorporatedherein by reference.

1. A structure comprising: an electronic device having an electronicallyactive portion having a surface; said surface has a dielectric layerhaving an opening therein exposing said electronically active portion;said opening having a perimeter; a layer of electrically conductivepolymer disposed on said dielectric layer; said layer of electricallyconductive polymer electrically contacts said electronically activeportion through said opening and overlapping said perimeter to bedisposed on said dielectric layer.
 2. A structure according to claim 1wherein said electronic device has a plural opening in said dielectriclayer, exposing a plurality of electronically active regions, saidelectrically conductive polymer electrically contacts said plurality ofelectronically active regions; said electrically conductive polymer hasportions joining said contacts to said exposed plurality ofelectronically active regions.
 3. A structure according to claim 1wherein said layer of electrically conductive polymer is in a pattern.4. A structure according to claim 1 wherein said electrically conductivematerial is selected from the group of one or more of substituted andunsubstituted polyparaphenylene vinylenes, polyparaphenylenes,polyanilines, polythiophenes, polyazines, polyfuranes, polypyrroles,polyselenophenes, poly-p-phenylene sulfides, polyacetylenes combinationsthereof and blends thereto with other polymers and copolymers of themonomers thereof.
 5. A structure comprising: a surface; a layer ofelectrically conductive polymer disposed on said surface in a pattern;at least one portion of said layer of electrically conductive polymer isin electrical contact with said surface; other portions of said layer ofelectrically conductive polymer are not in electrical contact with saidsurface.
 6. A structure according to claim 5 further including adielectric material disposed between said other portions and saidsurface.
 7. A structure according to claim 5 wherein said surface isselected from the group consisting of an electrical conductor and asemiconductor.
 8. A structure according to claim 7 wherein saidsemiconductor is formed from a material selected from the groupconsisting of an organic material and an inorganic material.
 9. Astructure according to claim 7 wherein said electrical conductor isformed from a material selected from the group consisting of a metal anda polymer
 10. A structure according to claim 1 wherein said electronicdevice is selected from the group consisting of a liquid crystal device,a transistor device and a light emitting device and a light absorbingdevice.
 11. A structure according to claim 10 wherein said transistor isselected from the group consisting of a bipolar transistor and a fieldeffect transistor.
 12. A structure according to claim 10 wherein saidlight emitting device is a light emitting diode.
 13. A structureaccording to claim 10 wherein said light absorbing device is a chargecoupled device.
 14. A structure comprising: an electrically conductivesurface having a peripheral edge; a layer of electrically conductivepolymer having a peripheral edge; said peripheral edge of saidelectrically conductive surface has regions that are not aligned to saidperipheral edge of said layer of electrically conductive polymer.15-112. (canceled)
 113. A structure comprising: an ohmic contact betweenan electrically conductive polymer and a semiconductor.
 114. A structureaccording to claim 113 wherein said semiconductor is selected from thegroup consisting of an organic semiconductor and an inorganicsemiconductor.
 115. A structure comprising: a low contact resistanceelectrical joint between a non-polymeric electrical conductor and anelectrically conductive polymer. 116-122. (canceled)
 123. A structurecomprising: a surface of a non-dielectric material; a layer of adielectric material having a first surface disposed on said surface of anon-dielectric material and having a second surface; said layer of saiddielectric material has an edge; a layer or electrically conductivepolymer disposed on said second surface and over said edge onto saidsurface of non-dielectric material. 124-131. (canceled)
 132. A structureaccording to claim 113 wherein electrically conductive polymer isselected from the group consisting of one or more of substituted andunsubstituted polyparaphenylene vinylenes, polyparaphenylenes,polyanilines, polythiophenes, polyazines, polyfuranes, polypyrroles,polyselenophenes, poly-p-phenylene sulfides, polyacetylenes combinationsthereof and blends thereof with other polymers and copolymers of themonomers thereof.
 133. A structure according to claim 113 wherein saidsemiconductor material is selected from the group consisting of anorganic and an inorganic material.
 134. A structure according to claim132 wherein said semiconductor material is selected from the groupconsisting of an organic and an inorganic material.
 135. A structureaccording to claim 115 wherein electrically conductive polymer isselected from the group consisting of one or more of substituted andunsubstituted polyparaphenylene vinylenes, polyparaphenylenes,polyanilines, polythiophenes, polyazines, polyfuranes, polypyrroles,polyselenophenes, poly-p-phenylene sulfides, polyacetylenes combinationsthereof and blends thereof with other polymers and copolymers of themonomers thereof.
 136. A structure according to claim 115 wherein saidsemiconductor material is selected from the group consisting of anorganic and an inorganic material.
 137. A structure according to claim135 wherein said semiconductor material is selected from the groupconsisting of an organic and an inorganic material.
 138. A structureaccording to claim 123 wherein electrically conductive polymer isselected from the group consisting of one or more of substituted andunsubstituted polyparaphenylene vinylenes, polyparaphenylenes,polyanilines, polythiophenes, polyazines, polyfuranes, polypyrroles,polyselenophenes, poly-p-phenylene sulfides, polyacetylenes combinationsthereof and blends thereof with other polymers and copolymers of themonomers thereof.
 139. A structure according to claim 123 wherein saidsurface of a non-dielectric material is a semiconductor materialselected from the group consisting of an organic and an inorganicmaterial.
 140. A structure according to claim 138 wherein saidsemiconductor material is selected from the group consisting of anorganic and an inorganic material.